Page 449 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

424 CHAPTER 2

VetBooks.ir 2.23

Fig. 2.23 A natural covering
of the Thoroughbred mare
shown in 2.2.

oestrous period, but where mares numbers are low If ovulation has occurred, then acceptable con-
this can be an economical approach. There are ception rates may still be achieved by breeding 12–18
some situations where the mares and the stallion hours after ovulation and the mare will usually stand
run together in the paddock for the breeding sea- to be mated. However, it has been shown that there
son. In both situations the mare is deemed ‘in-foal’ is a greater incidence of early embryonic loss associ-
if she does not return to oestrus. The risk of a twin ated with post-ovulation matings due to the fertilisa-
pregnancy that goes undetected is a weakness of this tion of an aged ovum.
system and, therefore, a refinement is that the mare It is important to restrain the mare adequately
is ultrasound scanned, for pregnancy diagnosis and for mating. A head collar and chain over the nose,
twin detection, when she does not return to oestrus a bridle or a chifney bit and/or a twitch can be used
or at 16–18 days after she was last mated (or seen to to keep the mare still. Some farms place hobbles on
be mated) and, subsequently, again at 28 days. the hindlimbs of the mare or tie up a forelimb. The
Those mares that tease positively are traditionally mare’s tail should be wrapped in a disposable ban-
bred on day 2 or 3 of oestrus and then every other dage. The perineal region should be washed with
day until the end of oestrus. In modern systems, mild soap and water before being rinsed and dried
the goal is to cover the mare as close to ovulation with paper towels. On some stud farms the stallion’s
as possible using the minimum number of attempts. penis is washed with warm water prior to and post
This decreases the amount of contamination in the breeding. More controversially, some stud farms use
mare’s reproductive tract and minimises use of the warm water and a mild soap to clean the penis, par-
stallion, helping to maintain stallion semen reserves ticularly at the start of the season or where the penis
and libido. is excessively dirty. Many clinicians believe this is
Mares should ideally be bred prior to ovulation contraindicated as it can alter the natural penile flora
when the mare has a dominant follicle (>30–35 mm) and risk unwanted bacterial overgrowth.
present but this requires ultrasound examination. One person should handle the stallion, one the
Ultrasound allows the number of matings to be lim- mare and a third, if available, should be there to assist
ited but requires that the reproductive tract should the stallion and check for ejaculation by palpating
be palpated daily to allow this. the urethral pulsations in the stallion. A good active